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BMW 3/20

The BMW 3/20 PS was the first BMW automobile designed entirely by BMW. It was manufactured from 1932 to 1934, replacing the 3/15 model that was initially an Austin 7 manufactured under licence from the Austin Motor Company.

Manufacturer

BMW

Also called

AM-1, AM-2, AM-3, AM-4

Production

1932 – 1934

Assembly

Eisenach, Germany

Predecessor

BMW 3/15

Successor

BMW 309

Class

City car

Body style

four seat saloon

four seat cabriolet

two seat convertible coupé

Layout

FR layout

Engine

788 cc (48.1 cu in) OHV straight-4

Transmission

4-speed manual

Wheelbase

2,150 mm (84.6 in)

Length

3,200 mm (126 in)

Width

1,420 mm (56 in)

Height

1,550 mm (61 in)

Curb weight

650 kg (1,433 lb) with saloon body

Designer(s)

Alfred Böning

The engine used in the 3/20 was based on the Austin Seven engine used in the 3/15, but its crankshaft ran in plain bearings instead of roller bearings and had an 80 mm (3.1 in) stroke, generating a displacement of 788 cc (48.1 cu in). The new engine design also had a water pump and an overhead valvecylinder head. These design changes caused the engine to generate 20 hp, but did not change the taxable horsepower rating of 3 PS, thus giving the model designation 3/20.

BMW 3/20 AM 4 engine

The 3/20 was larger than the 3/15, with an 84.6 in (2,149 mm) wheelbase and a body 3 in (76 mm) lower than the 3/15. The 3/20 used a backbone frame unrelated to the 3/15's Austin Seven "A" frame. It inherited the 3/15 DA-4's independent front suspension and added a swing axleindependent rear suspension, using a transverse leaf spring similar to that used at the front.The standard bodies for the car were built by Daimler-Benz in Sindelfingen.Journalist and engineer Josef Ganz, who had criticized the 3/15 DA-4's suspension system in the magazine Motor-Kritik, was contracted in July 1931 as a consultant in the design of the 3/20 AM-1.Four versions of the 3/20 were built: AM 1, AM 2, AM 3 and AM 4, where AM denoted Automobil München.